I'm a bit confused by the process of entangling photons emitted by two distinct qubits, wouldn't entangling those photons affect the state of the two original distinct qubits? Or is that simply how entanglement works?
Very naively, the following happens: Qubit A is entangled with Photon A. Qubit B is entangled with Photon B. Photon A and Photon B are measured together in way that does not permit distinguishing the two photons (this is where the magic happens) and destroyed. This results in Qubit A and Qubit B now being entangled.